animation reset

Ricardo Duarte
Ricardo Duarte Altair Community Member
edited July 3 in Community Q&A

Hello,

 

I am using motion view to see a system response to real-life dynamic data, for this I am using all 6 DoF of motion from the Global frame marker to a marker in my system.

I am inputing the motion from a ".cvs" file that I got from a real scenario. These go into the simulation as 2-D splines and are used in the motion for the acceleration of one marker relative to the other.

It runs as expected, but for some reason when the simulation reaches a specific point, the system resets to the initial position and keeps going from there until the end. See the video attached. sorry for low quality (the system moves in space, so the video needs to be zoomed out). 

What is this behaviour?

I am giving accelerations, it would not make sense to jump in this way, so the problem should not in the input file.

 

Also, as an unrelated question when I define a motion output (displacement, velocity or acceleration) what are the coordinates of the rotations (rotation vector or euler)?

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Answers

  • Chris Coker_20903
    Chris Coker_20903 Altair Community Member
    edited June 25

    A couple of thoughts:

    Plot your csv data and make sure it makes sense.  Pay special attention to the time vector.   Also preview the .csv curves once you've imported them into MotionView and make sure they still make sense.  It almost looks like there is a formatting issue with the time vector and that's what is making it jump.  But I would almost expect the solver to complain a lot (the acceleration to move the object back to that point would be very, very high, and therefore the forces would also be enormous.

    Look at the .log file and see if there are any interesting messages at the time when the object jumps back to the start.  That can also sometimes give some clues.

    One tip about using accelerometer data as input.  It almost always has some drift in it over time, and therefore isn't always that useful when I've tried to use it to directly drive an input into MBD models.  I have better results when I use a high pass filter to filter the drift, and then double integrate to get displacements, and then drive the model using displacements rather than accelerations.

  • GTT Adam
    GTT Adam
    Altair Employee
    edited June 25

    Hi Ricardo,

    Please review the time series results to see if this motion is actually occurring during the simulation or if it is perhaps just animation related. It is possible that the animation just needs to be reloaded. In a new instance, open HyperView and load in the H3D file to see if this repeat remains.

     

    Hope this helps!

    Adam Reid

  • Ricardo Duarte
    Ricardo Duarte Altair Community Member
    edited July 3

    Hello Adam and Chris,

     

    Thank you for the answers,

    • There is no problem with the time series.
    • The solver did not complaint as the output files do not show a displacement jump. And the jump itself could make sense if I was inputing displacement instead of accelerations
    • I do not really care about the drift as that is a "low frequency" effect, and I am mostly looking at the higher frequency part

    This problem was "solved" when I changed the interpolation of the data points from akima to cubic.

    I was led to assume it was a animation issue.

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